Through a comprehensive program of cellular and biochemical assays, I propose to measure and evaluate the potential for biological hazard resulting from the sunscreen agents, Escalol, 506, Escalol 507, and p-aminobenzoic acid, both alone and in combination with UV light. Specifically, I will assay a) the cytotoxicity of each of the compounds on normal human fibroblasts, XPA cells, and XPV cells and b) the UV interactive cytotoxic effects by either irradiation of the cells with UVA or UVB prior to sunscreen agent treatment or irradiation of the cells with UVA or UVB after sunscreen treatment and removal. I will also measure the induction of DNA repair synthesis in each of the two modes described above. The interaction of UVA (315-400 nm) and UVB (290-320 nm) with each of the sunscreens in the studies outlined above will be analyzed with attention focused upon recognizing any additive or synergic response. The in vitro tests will be designed to be as environmentally significants as possible through the use of biological doses of UVA or UVB (3-6 MED). In addition, each of the sunscreen agents will be analyzed in a bacterial mutagenesis system (Ames assay). Preliminary evidence suggests that some sunscreen agents may actually induce DNA repair synthesis. Additional studies are necessary to fully evaluate whether these sunscreen agents pose any biohazard to human cells.